Golf ball having dimples with constant dimple profile radius

ABSTRACT

Golf balls having outer surfaces with improved dimple patterns are provided. At least a portion of the dimples are spherical, and the spherical dimples have at least two different dimple diameters. Each spherical dimple has a radius of curvature that is substantially equal to the radius of curvature of every other spherical dimple on the outer surface of the ball. In another embodiment, the spherical dimples have at least three different dimple diameters. The spherical dimples having different dimple diameters also can have different edge angles, dimple depths, and/or dimple volumes. In one preferred embodiment, the maximum difference in radius of curvature between any two spherical dimples is less than or equal to 0.015 inches.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 63/123,031, filed Dec. 9, 2020, the entire disclosure of which is incorporated by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention generally relates to golf balls and more particularly to golf balls having outer surfaces with improved dimple patterns. At least a portion of the dimples are spherical, and the spherical dimples have at least two different dimple diameters. For an outer surface of a golf ball containing spherical dimples having at least two different diameters, each spherical dimple has a radius of curvature that is substantially equal to the radius of curvature of every other spherical dimple on the outer surface.

Brief Review of the Related Art

Golf balls generally include a spherical outer surface with a plurality of dimples formed thereon. Conventional dimples are spherical dimples with circular plan shapes that help reduce drag and increase lift of the golf ball. These dimples are formed where a dimple wall slopes away from the outer surface of the ball forming the depression.

Drag is the air resistance that opposes the golf ball's flight direction. As the ball travels through the air, the air that surrounds the ball has different velocities, thus different pressures. The air exerts maximum pressure at a stagnation point on the front of the ball. The air then flows around the surface of the ball with an increased velocity and reduced pressure. At some separation point, the air separates from the surface of the ball and generates a large turbulent flow area behind the ball. This flow area, which is called the wake, has low pressure. The difference between the high pressure in front of the ball and the low pressure behind the ball slows the ball down. This is the primary source of drag for golf balls.

The dimples on the golf ball cause a thin boundary layer of air adjacent to the ball's outer surface to flow in a turbulent manner. Thus, the thin boundary layer is called a turbulent boundary layer. The turbulence energizes the boundary layer and helps move the separation point further backward so that the boundary layer stays attached further along the ball's outer surface. As a result, there is a reduction in the area of the wake, an increase in the pressure behind the ball, and a substantial reduction in drag. It is the circumference of each dimple, where the dimple wall drops away from the outer surface of the ball, which actually creates the turbulence in the boundary layer.

Lift is an upward force on the ball that is created by a difference in pressure between the top of the ball and the bottom of the ball. This difference in pressure is created by a warp in the airflow that results from the ball's backspin. Due to the backspin, the top of the ball moves with the airflow, which delays the air separation point to a location further backward. Conversely, the bottom of the ball moves against the airflow, which moves the separation point forward. This asymmetrical separation creates an arch in the flow pattern that requires the air that flows over the top of the ball to move faster than the air that flows along the bottom of the ball. As a result, the air above the ball is at a lower pressure than the air underneath the ball. This pressure difference results in the overall force, called lift, which is exerted upwardly on the ball. The circumference of each dimple is important in optimizing this flow phenomenon, as well.

In addition to researching dimple pattern and size, golf ball manufacturers also study the effect of dimple shape, volume, and cross-section on overall flight performance of the ball. Conventional dimples are the shape of a section of a sphere. These profiles rely on essentially two independent parameters to fully define the dimple shape: diameter and depth (chordal or surface). Edge angle is often discussed when describing spherical dimple profiles but is not independent of diameter and depth.

Some conventional golf balls, especially those having spherical dimples, have kept variables (such as edge angle and chord depth) constant around the ball in an effort to improve the aerodynamic properties of the golf ball. These methods create a discontinuity of the curvature over the entire ball surface and may limit aerodynamic performance. Golf balls of the current invention comprise an outer surface having dimples, wherein at least a portion of the dimples are spherical and the spherical dimples have at least two different dimple diameters, wherein there is substantially no difference between the radius of curvature between any two spherical dimples. In one example, the spherical dimples have at least three different dimple diameters, wherein there is substantially no difference between the radius of curvature between any two spherical dimples. The air is thereby subjected to only two sources of curvature: the convex ball surface, and the concave dimple surface. The improved consistency in surface curvature may lead to a more consistent air flow and improved aerodynamic properties.

SUMMARY OF THE INVENTION

The present invention relates generally to a golf ball comprising an outer surface having dimples disposed thereon, wherein at least a portion of the dimples are spherical dimples. In one embodiment, the spherical dimples have at least three different dimple diameters. Each spherical dimple has a radius of curvature that is substantially equal to the radius of curvature of every other spherical dimple on the golf ball. In one preferred embodiment, the maximum difference in radius of curvature between any two spherical dimples is less than or equal to 0.015 inches. The outer surface of the ball can comprise both spherical and non-spherical dimples. The majority of dimples disposed on the outer surface of the ball can be spherical dimples. For example, the spherical dimples can comprise at least 66% of the total dimples on the outer surface of the golf ball. In another example, the spherical dimples can cover at least 78% of the outer surface of the golf ball. In yet another example, all of the dimples disposed on the outer surface of the ball are spherical dimples.

The spherical dimples having different dimple diameters also can have different edge angles, dimple depths, and/or dimple volumes. In one embodiment, the maximum difference in radius of curvature between any two spherical dimples is less than or equal to 0.010 inches. In another embodiment, the maximum difference in radius of curvature between any two spherical dimples is less than or equal to 0.005 inches.

The average radius of curvature (GPR) of all of the spherical dimples on the outer surface of the golf ball can be defined. Preferably, the GPR is within a range defined by the equation:

3.5116×10⁻⁶ n ²−3.5024×10⁻³ n+1.2568≤GPR≤8.4691×10⁻⁶ n ²−8.0284×10⁻³ n+2.5213

where n is the total number of dimples on the surface of the golf ball.

In one example, the spherical dimples on the outer surface of the golf ball have at least four different dimple diameters. In another example, the spherical dimples on the outer surface of the golf ball have at least five different dimple diameters.

In another embodiment of the golf ball, the spherical dimples have at least two different dimple diameters; each spherical dimple having a radius of curvature that is substantially equal to the radius of curvature of every other spherical dimple on the golf ball, and wherein the spherical dimples cover at least 74% of the outer surface of the ball.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features that are characteristic of the present invention are set forth in the appended claims. However, the preferred embodiments of the invention, together with further objects and attendant advantages, are best understood by reference to the following detailed description in connection with the accompanying drawings in which:

FIG. 1 is a dimple half-profile view showing the radial cross-sectional shape of a conventional dimple;

FIG. 2 is a schematic diagram showing an outer surface of a golf ball having two spherical dimples, wherein the dimples have different diameters and substantially the same radius of curvature in accordance with present invention; and

FIG. 3 is a side view of one embodiment of a golf ball having spherical dimples arranged on its outer cover in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a golf ball having a plurality of dimples on its surface separated by outer non-dimpled land surfaces. In the present invention, at least a portion of the dimples are spherical, and the spherical dimples have at least two different dimple diameters, wherein there is substantially no difference between the radius of curvature between any two such spherical dimples having the different diameters. That is, for an outer surface of a ball containing spherical dimples having at least two different diameters, each spherical dimple has a radius of curvature that is substantially equal to the radius of curvature of every other spherical dimple on the outer surface.

Referring to FIG. 1, a dimple half-profile view showing the radial cross-sectional shape of one spherical dimple formed on the surface of a golf ball is provided. The cross-sectional shape of the curved surface of the spherical dimple is a portion of a circle. Normally, the dimples of the present invention are spherical and have a diameter in the range of about 0.050 to about 0.250 inches and a dimple depth in the range of about 0.002 to about 0.020 inches. The surface of the golf ball may contain dimples having non-circular plan shapes rather than circular plan shapes. For example, the dimple plan shape may be triangular, rectangular, pentagonal, hexagonal, or any other suitable regular or irregular polygonal shape. In other embodiments, the golf ball surface may contain both dimples having circular and non-circular plan shapes. The total number of dimples can vary as is known in the art and is generally in the range of about 200 to about 600.

A plurality of such dimples is distributed over the outer surface of the golf ball. In general, dimples are formed in the golf ball surface as recesses or indentations. The cross-sectional shape of dimples is defined by a portion of a curved surface such as a circle, ellipse, or hyper-ellipse. Dimple cross-sectional shapes also include straight surfaces (i.e., conical, conical frustum, spherical-polygonal dimples, and the like). For example, for spherical dimples, the cross-sectional shape of the curved surface of the dimple is a portion of a circle.

Diameter measurements are determined on finished golf balls according to FIG. 1. Generally, it can be difficult to measure a dimple's diameter due to the indistinct nature of the boundary dividing the dimple from the ball's undisturbed land surface. Due to the effect of paint and/or the dimple design itself, the junction between the land surface and dimple may not be a sharp corner and is therefore indistinct. This can make the measurement of a dimple's diameter somewhat ambiguous. To resolve this problem, dimple diameter on a finished golf ball is measured according to the method shown in FIG. 1. Referring to FIG. 1, this Figure shows a dimple half-profile (34), extending from the dimple centerline (31) to the land surface (33) outside of the dimple. A ball phantom surface (32) is constructed above the dimple as a continuation of the land surface (33). A first tangent line T1 is then constructed at a point on the dimple sidewall that is spaced 0.003 inches radially inward from the phantom surface (32). T1 intersects phantom surface (32) at a point P1, which defines a nominal dimple edge position. A second tangent line T2 is then constructed, tangent to the phantom surface (32), at P1. The edge angle is the angle between T1 and T2. The dimple diameter is the distance between P1 and its equivalent point diametrically opposite along the dimple perimeter. Alternatively, it is twice the distance between P1 and the dimple centerline (31), measured in a direction perpendicular to centerline (31). The dimple depth is the distance measured along a ball radius from the phantom surface of the ball to the deepest point on the dimple. The chord plane runs through the point P1 and is normal to the dimple centerline 31. The chord depth is the distance from the chord plane to the deepest part of the dimple. The cap height is the distance from the chord plane to the phantom surface (32) along the dimple centerline (31). The dimple volume is the space enclosed between the phantom surface (32) and the dimple surface (34) (extended along T1 until it intersects the phantom surface).

In a preferred embodiment, the golf ball comprises an outer surface having a plurality of dimples, wherein at least a portion of the dimples have a spherical profile. The outer surface can include spherical and non-spherical dimples. In one particularly preferred embodiment, the majority of dimples are spherical. In one embodiment, the spherical dimples have at least two (2) different diameters. In another embodiment, the spherical dimples have at least three (3) different diameters. That is, there are preferably at least two or at least three different spherical dimple types (as grouped by diameter) on the outer surface of the golf ball.

As used herein, dimple diameters are considered different if they differ by 0.005 inches or greater. For example, spherical dimple type A may have a diameter of 0.155 inches, spherical dimple type B may have a diameter of 0.150 inches, and spherical dimple type C may have a diameter of 0.145 inches. Thus, in this example, dimple types A, B, and C would be considered to have different diameters. The golf balls of this invention comprise an outer surface having dimples, wherein at least a portion of the dimples are spherical, and the spherical dimples have at least two or at least three different dimple diameters, wherein there is substantially no difference between the radius of curvature between any two spherical dimples.

As customarily used in the art, the term, “radius of curvature” refers to the radius of an arc that best approximates the arc of the spherical dimple profile. FIG. 2 shows two spherical dimples (10, 12) on the same outer surface of a golf ball (14) of the present invention. The first spherical dimple (10) has a dimple diameter (d1) and radius of curvature (r). The second spherical dimple (12) has a different dimple diameter (d2) and an equivalent radius of curvature (r). Additionally, the first spherical dimple (10) and second spherical dimple (12) have different dimple depths and different edge angles.

In the present invention, each spherical dimple has a radius of curvature that is substantially equal to the radius of curvature of every other spherical dimple on the golf ball. In one preferred embodiment, the maximum difference in radius of curvature between any two spherical dimples is 0.015 inches or less. In one example, the maximum difference in radius of curvature between any two spherical dimples is 0.010 inches or less. In another example, the maximum radius of curvature between any two spherical dimples is 0.005 inches or less. The maximum radius of curvature difference for the spherical dimples is calculated by first determining the radius of curvature for each of the spherical dimples on the outer surface of the ball. The maximum radius of curvature difference is the difference between the largest radius of curvature and smallest radius of curvature for all spherical dimples on the outer surface of the golf ball.

In a preferred embodiment, every spherical dimple type (as grouped by diameter) has a different edge angle, chord depth, or dimple volume versus every other spherical dimple type. For example, spherical dimple type A has a diameter of 0.125 inches, spherical dimple type B has a diameter of 0.120 inches, and spherical dimple type C has a diameter of 0.115 inches; and each spherical dimple type (A, B, and C) has a different edge angle, chord depth, or dimple volume. The different spherical dimple types (A, B, and C) have different dimple diameters, and they preferably have one or more other distinctly different dimple features; namely a different edge angle, chord depth, and/or dimple volume. In one embodiment, the different spherical dimple types have two other different dimple features (for example, edge angle and chord depth). In another embodiment, the different spherical dimple types have three other different dimple features (for example, edge angle, chord depth, and dimple volume.)

The average radius of curvature of all spherical dimples on the outer surface of a golf ball is the Global Profile Radius (GPR) for the ball. The preferred GPR for the ball is a function of the total dimple count (including both spherical and non-spherical dimples), shown in Equations 1 and 2 below. Different Examples showing preferred ranges of GPR for different dimple counts are provided in Table 1 below. In the Examples shown in the following Table 1, at least a portion of the dimples on the outer surface of the golf ball are spherical-shaped. The spherical dimples are included in the Total Dimple Count (n).

TABLE 1 Lower Higher Total (Minimal) (Maximum) Dimple Value of Value of Count GPR Range GPR Range (n) (Inches) (Inches) 400 0.418 0.665 375 0.437 0.702 350 0.461 0.749 325 0.489 0.807 300 0.522 0.875 75 0.559 0.954

3.5116×10⁻⁶ n ²−3.5024×10⁻³ n+1.2568  Equation 1

where n is the total number of dimples on the surface of the golf ball.

8.4691×10⁻⁶ n ²−8.0284×10⁻³ n+2.5213  Equation 2

where n is the total number of dimples on the surface of the golf ball.

In a preferred embodiment, the Global Profile Radius (GPR) (in inches) follows Equations 1 and 2, such that it should be greater than or equal to the value obtained in Equation 1, and less than or equal to the value obtained in Equation 2, as set forth below in the mathematical relationship:

3.5116×10⁻⁶ n ²−3.5024×10⁻³ n+1.2568≤GPR≤8.4691×10⁻⁶ n ²−8.0284×10⁻³ n+2.5213

where n is the total number of dimples on the surface of the golf ball.

Thus, in an example, where the ball has 100 total dimples, n in the Equation above would have a value of 100 and the Equation would be used to calculate a lower limit of 0.942″ (lower (minimal) value of GPR Range) and an upper limit (lower (minimal) value of GPR Range) of 1.803″ for the GPR of the dimples on the golf ball. That is, for a 100-dimple golf ball, if we average the radii of curvature for all the spherical dimples, that average value should be greater than or equal to 0.942″ (the ‘lower’ value) and less than or equal to 1.803″ (the ‘higher’ value).

While the present invention is not limited by any particular dimple pattern, in one embodiment, dimples having a perimeter and a surface shape defined according to the present invention are arranged along parting lines or equatorial lines, in proximity to the poles, or along the outlines of a geodesic or polyhedron pattern, and dimples that do not have a perimeter and a surface shape defined according to the present invention occupy the remaining spaces. In another embodiment, dimples that do not have a perimeter and a surface shape defined according to the present invention are arranged along parting lines or equatorial lines, in proximity to the poles, or along the outlines of a geodesic or polyhedron pattern, and dimples that have a perimeter and a surface shape defined according to the present invention occupy the remaining spaces. Suitable dimple patterns include, but are not limited to, polyhedron-based patterns (e.g., icosahedron, octahedron, dodecahedron, tetrahedron, icosidodecahedron, cuboctahedron, and triangular dipyramid), phyllotaxis-based patterns, spherical tiling patterns, and random arrangements.

The dimples of the present invention may be used with practically any type of ball construction. Golf balls having various constructions may be made in accordance with this invention. For example, golf balls having one-piece, two-piece, three-piece, four-piece, and five or more-piece constructions wherein the term “piece” refers to any core, intermediate (casing) layer, or cover, or other component of a golf ball construction. For example, in one version, a one-piece ball, wherein the entire ball is made of one-piece, excluding any paint or coating and indicia applied thereon. In another example, a two-piece ball comprising a single core and a single cover layer can be made. In a third version, a three-piece golf ball containing a dual-layered core and single-layered cover can be made. The dual-core includes an inner core (center) and surrounding outer core layer. In another version, a three-piece ball containing a single core layer and two cover layers can be made. In yet another version, a four-piece golf ball containing a dual-core and dual-cover (inner cover and outer cover layers) can be made. In yet another construction, a four-piece golf ball containing a core; an inner cover layer, an intermediate cover layer, and an outer cover layer, may be made. In still another construction, a five-piece ball is made containing a dual-core, an inner cover layer, an intermediate cover layer, and an outer cover layer. The diameter and thickness of the different layers along with properties such as hardness and compression may vary depending upon the construction and desired playing performance properties of the golf ball.

Different materials may be used in the construction of the golf balls in the present invention. For example, the cover of the ball may be made of a thermoset or thermoplastic composition. A castable or non-castable polyurethane or polyurea, an ionomer resin such as an ethylene acid copolymer ionomer, or any other suitable cover material known to those skilled in the art may be used to construct the cover of the golf ball. The covers may be single or multi-layered and made of a durable material such as ethylene acid copolymer ionomers or thermoplastic or thermoset polyurethanes. Normally, the core layers are made of a highly resilient natural or synthetic rubber material such as styrene butadiene, polybutadiene, polyisoprene, or ethylene acid copolymer ionomers. The rubber composition contains a mixture of ingredients including free-radical initiator such as peroxides, cross-linking co-agents such as zinc diacrylate (ZDA), and additives. Also, there may be intermediate (casing) layers disposed between the core and cover.

The present invention is illustrated further by the following Examples, but these Examples should not be construed as limiting the scope of the invention.

EXAMPLES Example 1

Referring to FIG. 3, a golf ball cover (20) having a dimple pattern (22) is shown. The pattern is a tetrahedron dimple pattern with 352 spherical dimples having four different dimple diameter sizes. That is, all of the dimples on the outer surface of this golf ball example have a spherical profile. The dimple pattern is designed such that all of the spherical dimples have substantially the same radius of curvature, and the dimple depths, dimple volumes, and edge angles are different as shown in Table 2. That is, in this Example, the spherical dimples have four different dimple diameter sizes, and the maximum difference in radius of curvature between any two dimples is 0.011 inches, meaning each spherical dimple has a radius of curvature that is substantially equal to the radius of curvature of every other spherical dimple on the outer surface of the golf ball. The spherical dimples, having the four different dimple sizes, also have different dimple depths, dimple volumes, and edge angles. Based on Equations 1 and 2, the preferred Global Profile Radius (GPR) for a dimple pattern with 352 spherical dimples is between 0.459 inches and 0.745 inches, and this example has a GPR equal to 0.570 inches.

TABLE 2 Dimple Diameter Quantity Dimple Edge Dimple Depth Dimple Radius of Curvature Dimple (Inches) on Ball Angle (Inches) Volume (Inches) A 0.130 48 11.00 0.0062 4.148 × 10⁻⁵ 0.568 B 0.160 120 13.50 0.0094 9.499 × 10⁻⁵ 0.572 C 0.170 72 14.50 0.0108 1.224 × 10⁻⁴ 0.562 D 0.175 112 14.75 0.0113 1.359 × 10⁻⁴ 0.573

When numerical lower limits and numerical upper limits are set forth herein, it is contemplated that any combination of these values may be used. Other than in the operating examples, or unless otherwise expressly specified, all of the numerical ranges, amounts, values and percentages such as those for amounts of materials and others in the specification may be read as if prefaced by the word “about” even though the term “about” may not expressly appear with the value, amount, or range. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention.

It is understood that the compositions, ball components, ball structures, and finished golf balls described and illustrated herein represent only some embodiments of the invention. It is appreciated by those skilled in the art that various changes and additions can be made to compositions and products without departing from the spirit and scope of this invention. It is intended that all such embodiments be covered by the appended claims. 

We claim:
 1. A golf ball comprising an outer surface having dimples disposed thereon, wherein at least a portion of the dimples are spherical dimples and wherein the spherical dimples have at least three different dimple diameters; each spherical dimple having a radius of curvature that is substantially equal to the radius of curvature of every other spherical dimple on the golf ball.
 2. The golf ball of claim 1, wherein a maximum difference in radius of curvature between any two spherical dimples is less than or equal to 0.015 inches.
 3. The golf ball of claim 1, wherein a majority of dimples disposed on the outer surface of the golf ball are spherical dimples.
 4. The golf ball of claim 3, wherein the spherical dimples comprise at least 66% of the total dimples on the outer surface of the golf ball.
 5. The golf ball of claim 3, wherein the spherical dimples cover at least 78% of the outer surface of the golf ball.
 6. The golf ball of claim 1, wherein all of the dimples disposed on the outer surface of the golf ball are spherical dimples.
 7. The golf ball of claim 1, wherein the outer surface of the golf ball comprises spherical and non-spherical dimples.
 8. The golf ball of claim 1, wherein the spherical dimples having different dimple diameters also have different edge angles.
 9. The golf ball of claim 1, wherein the spherical dimples having different dimple diameters also have different dimple depths.
 10. The golf ball of claim 1, wherein the spherical dimples having different dimple diameters also have different dimple volumes.
 11. The golf ball of claim 1, wherein a maximum difference in radius of curvature between any two spherical dimples is less than or equal to 0.010 inches.
 12. The golf ball of claim 11, wherein the maximum difference in radius of curvature between any two spherical dimples is less than or equal to 0.005 inches.
 13. The golf ball of claim 1, wherein the average radius of curvature (GPR) of all of the spherical dimples on the outer surface of the golf ball is within a range defined by the equation: 3.5116×10⁻⁶ n ²−3.5024×10⁻³ n+1.2568≤GPR≤8.4691×10⁻⁶ n ²−8.0284×10⁻³ n+2.5213 where n is the total number of dimples on the surface of the golf ball.
 14. The golf ball of claim 1, wherein the spherical dimples on the outer surface of the golf ball have at least four different dimple diameters.
 15. The golf ball of claim 14, wherein the spherical dimples on the outer surface of the golf ball have at least five different dimple diameters.
 16. A golf ball, comprising an outer surface having dimples disposed thereon, wherein at least a portion of the dimples are spherical dimples and wherein the spherical dimples have at least two different dimple diameters; each spherical dimple having a radius of curvature that is substantially equal to the radius of curvature of every other spherical dimple on the golf ball, and wherein the spherical dimples cover at least 74% of the outer surface of the golf ball.
 17. The golf ball of claim 16, wherein a maximum difference in radius of curvature between any two spherical dimples is less than or equal to 0.015 inches.
 18. The golf ball of claim 16, wherein the spherical dimples having different dimple diameters also have different edge angles.
 19. The golf ball of claim 16, wherein the spherical dimples having different dimple diameters also have different dimple depths.
 20. The golf ball of claim 16, wherein the spherical dimples having different dimple diameters also different dimple volumes.
 21. The golf ball of claim 16, wherein a maximum difference in radius of curvature between any two spherical dimples is less than or equal to 0.010 inches.
 22. The golf ball of claim 21, wherein the maximum difference in radius of curvature between any two spherical dimples is less than or equal to 0.005 inches. 